The absence of impediments

The sixth: The absence of impediments,And by that we mean: namely menstruation and post-natal bleeding,Meaning: that it is not obligatory for a menstruating woman to fast, nor for a woman with post-natal bleeding; rather, if they were to fast, it would be forbidden for them and their fast would be invalid, based on the saying of the Prophet (peace and blessings be upon him), affirming the ruling for the menstruating woman: “Is it not the case that when she menstruates, she does not pray and does not fast?”The women said: “Yes.”
These are the conditions for the obligation of performing the fast.